Without exception, various existing commercial processes for oxidation of hydrocarbons (e.g., aromatic hydrocarbons such as cumene hydroperoxide (hereinafter “CHP”), etc.), by their very technical configuration comprise barbotage-based processes, in which an oxidizing agent (typically air or air-oxygen) is passed through a layer of the liquid phase of the hydrocarbons being oxidized by way of barbotage (i.e., by formation and movement of air bubbles therethrough).
Accordingly, the conventional oxidation reactors are almost completely filled with the liquid phase which comprises a mixture of the product being oxidized, and of oxidation reaction by-products (e.g., hydroperoxides and by-products). The gas phase—the air delivered to the reactor, and the off-gas exiting the reactor (having a lower oxygen concentration)—takes up a relatively small portion of the surrounding liquid phase (e.g., approximately 8% of volume), and therefore typically only occupies approximately 15% of the overall reactor volume. Air (i.e., the gas phase) is typically fed through the bottom portion of the reactor through a bubble distributor component configured to minimize the size of the air bubbles passing therethrough.
As the air bubbles rise upward through the liquid phase (which almost completely fills the reactor), they transfer the gas phase oxygen (O2gas) to the liquid phase of the products being oxidized, while simultaneously being dissolved therein. Unfortunately, this approach, involving barbotage of air through a liquid phase, does not forbid an increase of the total surface area of the gas phase bubbles, and accordingly, prohibits the desirable increase in the speed of the reaction of formation of the hydroperoxide product, and thus also limits the ability to raise process selectivity, at least for the following reasons:                (1) The high speed at which the air bubbles rise upward through the height of the reactor, and        (2) Strict safety protocols regarding limitations of oxygen concentration in the off-gas.        
In any barbotage-type oxidation process, oxygen (O2gas), is primarily expended in the course of formation of reaction by-products, and is only partially expended in formation of the desired product—hydroperoxide. Moreover, in barbotage-type oxidation processes, at least a portion of the oxygen (O2gas) is actually expended in the course of formation of undesirable reaction by-products that in fact serve as oxidation reaction inhibitors.
All of the above factors, in concert, lead to an insufficient level of conversion of the hydrocarbon being oxidized, and significantly lower process selectivity. As a result, previously known commercial processes have been unable to achieve a sufficiently high hydroperoxide concentration and selectivity in their oxidation reaction output products. For example in commercial barbotage processes involving oxidation of cumene, the maximum obtained concentration of the CHP product does not exceed 35% mass, while in processes involving oxidation of sec-butylbenzol, the concentration of the obtained hydroperoxide does not exceed 8%-10% mass. However, without exception, even if an increase in the conversion of the initial hydrocarbons (and, correspondingly, an increase in hydroperoxide concentration), is somehow obtained, it is only at the expense of considerable decrease in process selectivity, to a level practically unacceptable for commercial processes.
Irrespective of the chemical composition of the product being oxidized, the differences between existing barbotage-based oxidation processes are not sufficient to be considered as fundamental. For example, in a process of oxidizing of cumene into CHP, various barbotage-based processes comprise the following variations/differences therebetween:
(1) Differences in process temperature:                (a) low temperature process: from 80° C. to 95° C., which predetermines and necessitates the use of enormous reactors in process implementation;        (b) medium temperature process: from 95° C. to 115° C.; and        (c) high temperature process: from 115° C. to 130° C.;        
(2) Differences in pressure implemented in process reactors:                (a) low pressure: from 1.2 to 1.5 atm.;        (b) medium pressure: from 4 to 5 atm.; and        (c) high pressure: from 6 to 7 atm.        
(3) Differences in alkaline agent being utilized:                (a) NaOH or a mixture of NaOH with NH4OH—the so-called “dry oxidation process”; and        (b) Water solution of Na2CO3 and Na2CO3 together with NH4OH—the so-called “wet (or water-emulsion) oxidation process”.        
The maximum selectivity that has been achieved in practice to date in barbotage-type cumene oxidation processes has not exceeded about 95% mol. with conversion of cumene not exceeding about 30% mol.—moreover, further increases in conversion of cumene (and correspondingly, in the concentration of CHP), has lead to a catastrophic increase in formed amounts of undesirable by-products, and a drop in process selectivity.
In oxidation of other hydrocarbons, for example, aromatic hydrocarbons, such as ethylbenzol and sec-butylbensol, the conditions are much more severe—the reaction temperature and pressure are higher, and the alkaline agent is delivered to the reaction is much higher than in cumene oxidation processes, while the ranges of the above-noted key process parameters are much more narrow.
Accordingly, the essence of conventional commercial technologies remains unchanged—namely, the barbotage of air through a liquid phase of the hydrocarbons being oxidized, with the hydrocarbons' inexorably low conversion in view of the significant inhibition of the process by the resulting reaction by-products. And, as was noted above, the key commonality between all previously known barbotage-based processes is their inevitably low conversion of the hydroperoxides being oxidized, and their fundamental inability to obtain hydrocarbons having practically no reaction byproducts.
It would thus be desirable to provide a process of oxidation of hydrocarbons, that enables significantly higher selectivity, a greater level of safety, lower capital costs, etc., than conventional oxidation processes utilizing the barbotage technique.